Much of the investigators analysis of the developmental mechanisms of neural tube defects (NTDs) will use the mouse as a model system. Some of the research will examine the molecular and cellular basis of NTDs in existing mouse NTD mutant strains. Other experiments will manipulate signaling pathways via transgenesis to address specific hypotheses about the roles of these pathways in the ontogeny of normal neurulation and NTDs. Although mouse work is expensive relative to most embryological models, the Core will make the investigators= research much more cost-effective than if each investigator of the program were to have an individual colony. All of the mouse strains needed are likely to be used by two or more projects, allowing fewer cages and less maintenance. A Core technician will decrease and streamline the mouse husbandry work-load by providing common services. Production of transgenics by the Core eliminates the need for each project to set up and learn the production system. The Core will provide the following resources and services: (1) Production of wildtype embryos and chimeric mice: The Core will provide embryos on demand from timed matings of wildtype outbred mice. Midgestation embryos will be provided for adhesion assays, in situ hybridization, immunohistochemistry, and cell death/proliferation assays. Early embryos will be produced for use in morula aggregation, blastocyst ES cell injection, and DNA pronuclear injection. A colony of vasectomied males will be used to induce pseudopregnancy in a population of females to be used as recipients of embryo transfers. Additional females will be required for mating to chimeras and for amplification of outbred stocks. (2) Maintenance of mutant and transgenic stocks: The Core will maintain all the mutant and transgenic stocks used and made by the various Components. Per the instructions and oversight of the Component staff, stocks for a given Component will be maintained in the numbers required for successful execution of experiments. Core services will include setting up matings, splitting cages, weaning, culling, taking biopsies for genotyping, and preparation of genomic DNA. Genotyping by DNA analysis will be performed in collaboration with Component staff. (3) Generation of mutant and transgenic embryos: Working in close collaboration with Component staff, the Core will assist in the generation of mutant and transgenic embryos for experimental analysis. Timed matings will be set up and plugs checked daily. Core staff will assist in the dissection of mutant embryos at the desired stage.